Electronic governor for internal combustion engine

ABSTRACT

To provide for speed governing of internal combustion engines having an electronic fuel control, typically an electronic fuel injection system in which the pulse duration of generated injection control pulses determines the amount of fuel being supplied, in a given time, to the engine, a pulse source generates a series of pulses at a frequency determinative of maximum speed of the engine. This frequency is compared with a frequency representative of actual engine speed and, when the actual speed frequency exceeds the maximum generated speed frequency, a switch (typically a flip-flop) is controlled to change state, the switch being connected to interrupt fuel injection pulses, thereby cutting fuel from the engine. Preferably, the comparator includes an EXCLUSIVE OR-gate.

COMBUSTION ENGINE United States Patent 1 91 1111 3, Kiencke et al. Nov.4, 1975 [5 ELECTRONIC GOVERNOR FOR INTERNAL 3,757,571 9/1973 Chamberas123/118 Primary ExaminerCharles J. Myhre [75] Inventors: Uwe Kiencke,Moglingen; Martin Zechnall, Schwieberdingen, both of AssistantExaminer-Ronald COX Germany Attorney, Agent, or FzrmF1ynn & Frlshauf[73] Assignee: Robert Bosch GmbH,

Gerlingen-Schillerhohe, Germany ABSTRACT [22] Filed: June 12, 1974 Toprovide for speed governing of internal combustion engines having anelectronic fuel control, typically an [21] APPI' N05 478,594 electronicfuel injection system in which the pulse duration of generated injectioncontrol pulses determines [30 Foreign Application priority Data theamount of fuel being supplied, in a given time, to the engine, a pulsesource generates a series of pulses July 12, 1973 Germany 2335440 at afrequency determinative of maximum Speed of the 52 us. c1. 123/198 DB-123/32 EA' 123/118 i frequency COTTPaYCd with a frequency [51] Int C12 677/00 1502? 9/00 representative of actual engine speed and, when the Sactual speed frequency exceeds the maximum gener- [58] Field of 23/32198 DB ated speed frequency, a switch (typically a flip-flop) iscontrolled to change state, the switch being connected [56] ReferencesClted to interrupt fuel injection pulses, thereby cutting fuel 1 UNITEDSTATES PATENTS from the engine. Preferably, the comparator includes3,572,302 3/1971 Wollesen 123/118 an EXCLUSIVE OR-gate. 3,651,793 3/1972Roth 123/32 EA 3,659,571 5/1972 Lang 123/102 7 Claims, 1 Drawing Figure"FUEL "FUEL INJECTION INJECTION TERMINATE START PULSE PULSE 0 ENGINEPULSE SCANNING COMPARATOR 301 3 i SPEED CIRCUITS STAGE FREQUENCY i a j150 171 I I 293 29] 296 51 B I "i5 (170 1 l 5 E D I' 11 111 153 62 M I 1J 31, 1 I K "TX 1.1 32 STROBE 158 62 D 0 I I I 300 O2 REFERENCE I D 1173 I I 292 f f I 15% (MAXIMUM SPEEDl' 172 [172 l CLOCK FREQUENCYELECTRONIC GOVERNOR FOR INTERNAL COMBUSTION ENGINE The present inventionrelates to a governing system for internal combustion engines andparticularly to such a system which can be combined with a fuelinjection system described, for example, in US. Pat. No. 3,483,851,Reichardt, assigned to the assignee of the present application.

The speed of internal combustion engines depends, at a given load, onthe amount of fuel being supplied. Frequently there is a time delaybetween change in loading and supply of fuel or, for some other reasonfor example malfunction of control systems or the like, excessive fuelmay be supplied. This may cause the engine to run faster than desired.Particularly modern internal combustion engines can easily reach speedsin excess of maximum design speed, without any indications to the engineoperator, such as excessive noise, valve chatter or the like beingapparent. It is therefore frequently necessary to include a maximumspeed governing arrangement in any control system for an internalcombustion engine. lntemal combustion engines, in which the fuel supplyis controlled electronically, permit electronic governing since signalsrepresentative of engine operation are already available in theelectronic fuel supply control system.

Governing systems have been proposed which prevent excessive fuelsupply, typically excessively long opening times of fuel injectionvalves under given load conditions, by using analog computation circuitsto prevent excessive engine speeds and, particularly, run-away of theengine. Such analog computation systems or circuits are not suitable,however, when com bined with an internal combustion engine controlsystem which uses a digitally operating circuit, particularly anincremental digital circuit.

It is an object of the present invention to provide a speed governingsystem for internal combustion engines which are controlled by means ofdigital controllers, and more particularly digital controllers using incremental digital circuits controlling the opening time. or duration offuel injection valves.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, a comparator stage isprovided to compare a frequency proportional to speed of the engine withanother frequency which is pre-set and is representative of maximumpermissible engine speed. When the frequency, and particularly whenusing pulse techniques, the pulse repetition rate (PRR) of the enginespeed signal exceeds the frequency (or the PRR) of the reference orgoverning command frequency, a signal is ob tained at the comparatorstage which is transmitted to a controlled switch, typically a JKflip-flop, the switch (i.e. the FF) changing state and, due to itsconnection, interrupting the injection pulse.

In a preferred form, the comparator state is an EX- CLUSIVE OR-gate,each input to which has a time di vision, or strobing, or time scanningcircuit connected thereto.

The arrangement has the particular advantage that a fair number of thecircuit elements, and the signals required to control the arrangement,are already present in digital incremental internal combustion enginecontrol systems. The governing arrangement can. there- 2 fore, be easilyand simply constructed by minor modification, or addition to alreadypresent circuit components.

The invention will be described by way of example with reference to theaccompanying drawings, wherein the single FIGURE illustrates a schematicblock diagram of a digital speed governing arrangement for an internalcombustion engine fuel injection system.

Output pulses f3 are applied to a terminal 62, representative of speedof the engine. These pulses may be derived, as shown schematically, by atachometer generator 41, connected to the crankshaft 40 of the engine(not shown). Speed signals, in digital form, are available in electronicfuel injection systems. The speed signal pulses f3, at terminal 62, areapplied to the D input of a first D flip-flop (FF) 167, which forms partof a first time scanning stage 97. The first time scanning stage 97further includes a second D-FF 170, the D input of which is connected tothe output Q1 of the first D-FF 167. The output Q2 of the second D-FF isconnected to one input of an NAND-gate 171. The out put Q1 of the firstD-FF 167 is connected to the other input of the NAND-gate 171.

An oscillator, providing pulses at a PRR corresponding to the highestpermissible speed of the internal combustion engine is connected toterminal 62a of a second time scanning circuit 970. The second timescanning circuit 97a is, generally, similar to the first time scanningcircuit 97. Two D-FFs 172a and 172 as well as a NAND-gate 173 areconnected identically to the connection of the first time scanning stage97.

An input terminal 168 is connected to an inverter 169, the inverterbeing connected to the clock inputs of the four D-FFs 167, 170, 172a,172. The input terminal 168 has a clock frequency applied thereto. Thisclock frequency is readily available in digital circuits, particularlyin incremental digital circuits, in which a stepping clock generatorprovides for uniform, even stepping of the incrementally operatingcircuit.

The two time scanning circuits 97, 97a are then connected to acomparator stage 98a. Comparator stage 98a is constructed as a modifiedexclusive OR-gate. It has an input AND-gate 291 to which the directoutput from NAND-gate 173 is connected as well as the inverted outputfrom NAND-gate 171, over an inverter 293. A second input AND-gate 292 isprovided, connected in complementary manner to AND-gate 291, that is,having the output of NAND-gate 171 applied and the inverted output fromNANDgate 173, over an inverter 294. The comparator stage 980 furtherincludes a J K-F F 295. The strobe, or clock pulse terminal of the FF295 is connected to terminal 168a, to which a clock frequency or clockpulse sequence is connected. The JK-FF 295 operates as a pulsecorrecting stage. Its J input is connected to the output of AND- gate291. Its K input is connected to the output of AND-gate 292.

The positive or Q1 output of the J K-FF 295 is connected to an AND-gateto which further the output from AND-gate 291 is connected as a secondinput. The gates, and the FF, together, form the comparator stage.

The output from the comparator stage, that is. the output from AND-gate296, is connected to the first input of an OR-gate 300. The second inputof OR-gate 300 is connected to a terminal 301. Terminal 301 is connectedto the digital electronic circuit for a fuel injection system. Thisdigital electronic circuits provides a stop or terminate pulse atterminal 301 when a previously commanded fuel injection pulse is to beterminated. Some fuel injection systems provide a pulse, the duration ofwhich determines the opening time of a fuel injection valve. Othersystems provide a pulse when the valve is to be opened, and anotherpulse when the valve is to close. The second type system can readily beinstrumented from the first type by differentiating the fuel injectionvalve opening pulse, first in one direction (when the pulse starts) andthen by differentiating the trailing flank of the pulse, that is,differentiating with respect to the other direction, to obtain the fuelinjection terminate pulse. It is this type of pulse which is applied toterminal 301. This pulse can be derived, therefore, for example from thetype of electronic circuit disclosed in the foregoing patent; in anincrementally, digitally operating fuel injection control system, theterminate pulse would be directly available.

The output of the OR-gate 300 is connected to the K input of a secondJK-F F 152. The J input of the FF 152 is connected to a switch 150 andthen to a terminal 302. Terminal 302' has a constant l-signal applied,which is transferred over switch 150 when the switch is closed, whichoccurs over a predetermined portion of crankshaft revolution. Terminal302 likewise is connected to the electronic control system for the fuelinjection valve and provides the signal which enables the fuel injectionvalve of the injection system to be open. Terminal 302 or terminal 302'in connection with switch 150 may be used alternatively.

The switch 150 is periodically opened and closed by a cam 151, connectedto the crankshaft of the engine and operating in synchronism therewith.When closed,

it applies a l-signal to the J input of FF 152. The clock pulse input ofthe FF 152 is connected to a clock pulse terminal 168b, to which afurther clock pulse frequency is connected. The direct output Q1 of FF152 is connected to the input of a power amplifier 153 which controlsfrom its output terminal 134 the energization of the magnet or solenoidwinding 32 of a fuel injection valve. Only one such winding is shown asan example for all the injection valves associated with all thecylinders. In many systems it is sufficient that all injection valvesopen and close simultaneously, although they may be associated withdifferent cylinders.

Operation: Thebasic principle of the system is based on comparing anengine speed frequency f derived from a tachometer generator 41, coupledto the engine, with a fixed or reference frequency f, which correspondsto the maximum permissible speed of the engine. These two pulsesequences, or frequencies, are scanned or strobed in the circuits 97,97a and compared in the comparator stage 98a. If the speed of the engineexceeds the highest maximum speed, the sign of the pulses at the outputof thecomparator stage 98 will reverse, and a pulse applied to the Jinput of the FF 152, by providing a pulse to the K input of FF 152,similar to the terminate pulse, immediately interrupts a previouslytriggered or started fuel injection pulse by re-setting of the FF 152.

The circuit components, themselves, are well known and reference may behad, for example, to Logic Handbook, by Digital Equipment Corporation,1968, which describes digital components, including the flipflops inquestion. The D-type FF, such as FF 167, 170; 1720, 172, usessingle-ended data inputs, connected to the D terminal, has an additionalclock input and is'triggered or provides an output on the flank or edgeof the clock pulse provided that the D input has a l-signal applied. Theleading, or trailing flank of the pulse may be selected by suitableconnecting circuitry. The JK-FF, such as FF 295, or 152, is also aclocked general-purpose FF which, however, has two inputs which arecomplementary. Either the J, or the K input can have a l-signal appliedand upon the occurrence of the clock pulse connected to the clock pulseinput (terminals 168a, 1681)), the FF will assume the state commanded bywhether the J, or K input has a l-signal applied, and

provide a l-signal at the Q1 output, or, respectively, at thecomplementary, or Q2 output. Of course, if the complementary output hasa l-signal, the other output has a O-signal. These outputs will remainuntil there is a change in input signals which will be transferred tothe output of the occurrence of the next clock pulse. Timing relationsand details are well known, and reference may be made to theaforementioned publication.

Operation of pulse scanning circuits 97, 97a: An input pulse f3 onterminal 62 is transferred through the FF 167 upon occurrence of thenegative flank of the immediately succeeding strobe pulse from terminal168. Upon occurrence of the next following strobe pulse applied fromterminal 168 over the inverter 169, the ouput pulse from FF 167 istransferred through the FF 170. The NAND-gate 171 provides a negativeoutput pulse when the input pulse f3 was transferred through the firstD-FF 167, but not yet to the second D-FF 170. The pulse duration of theoutput pulse of the NAND-gate 171 thus is equal to the pulse duration ofthe strobe frequency at terminal 168. The D-FF is generallycharacterized by the fact that a signal at its D, or data input istransferred at the next occurring clock pulse to theoutput Q1.

The pulse duration of the pulses derived from the NAND-gates 171, 173 isthus equalized; comparison of the pulse repetition rate (PRR) orfrequency of the pulse train supplied by the NAND-gates 171, 173 is donein the comparator stage 980. The O-pulses at the outputs from theNAND-gates 171, 173 are inverted in the inverter stages 293, 294,respectively, into l-pulses. The l-pulses derived from the outputs ofthe inverters 292, 293 are not transferred through the AND-gates 291,292, however, under usual conditions. Let it be assumed that inverter293 provides a l-signal. The

AND-gate 291 can transfer this l-signal only if, simultaneously, theNAND-gate 193 provides a l-signal. This, however, is the case onlyduring a pulse interval of the pulse from NAN D-gate 193. The JK-FF 295,in cooperation with the AN D-gate 296, provides for pulse correction.The signals at the inputs J, K of the .lK-FF 295 are transferred to theQ1 output only upon occurrence of the next clock pulse from clockterminal 1683. The first positive pulse at the output of the AND-gate291 thus does not provide a l-signal at the output of the AND-gate 296.Only if a second pulse, to be counted in the same direction, isprovided, will both inputs of the AN D-gate 296 have l-signals applied.Thus, if the speed of the engine exceeds the highest permissible level,terminal 62 will have more pulses applied thereto than the referencefrequency terminal 62a. This increase in pulses results in l-signals atthe output of the AND-gate 291. If at least two extra l-signals occurthereat, the output of the AND-gate 296 will likewise have a l-signalarise thereat which is transferred over the OR-gate 300 to the K inputof the second JK-FF 152.

The timing of a single injection cycle will now be described. It is,again, assumed that the injection valves of the engine are all triggeredsimultaneously; that is, that their windings are all in parallel to the'winding 32. Common triggering of all injection valves is customary inmany fuel injection systems.

At a predetermined angle of the crankshaft, switch 150 is closed by thecam 151. A l-signal is thus applied to the J input of the JK-FF 152. Atthe next following clock pulse from clock terminal 168b, the FF 152 istriggered or placed in the state which provides a l-signal at the directQ1 output. The l-signal at the Q1 output is amplified in the poweramplifier 153 and applied to the winding 132, thus opening winding 132.Let it be assumed that the engine operates below the highest permissiblespeed. The output of the AND-gate 296 will thus have a O-signal. Theinjection pulse is then terminated only when the fuel injectionterminate pulse is applied to terminal 301 from the fuel injectionsystem. This pulse will be applied to the K input of the FF 152. At thenext following clock pulse from the clock 168b, the FF 152 is re-set,providing a O-signal at the direct Q1 output of FF 152, disablingamplifier 153 and deenergizing the solenoid 32. Fuel injection is thusterminated.

If the highest speed is exceeded then, as above described, a l-signa]will appear at the output of the AND-gate 296 which is applied to the Kinput of FF 152. Fuel injection is thus immediately interrupted. If thespeed should have been too high at the beginning of the injection cycle,fuel injection will nevertheless be started at the occurrence of thefirst clock pulse from clock 168 after closing of switch 150 but will beimmediately interrupted at the occurrence of the next succeeding clockpulse at terminal 168b. Very little fuel will thus be injected and thespeed of the engine will rapidly decrease.

Various changes and modifications may be made within the scope of theinventive concept.

The rates of the clock pulses at the strobe terminal 168, and at theclock terminals 168a, 168b may be suitably selected, (i.e. the basicclock frequency of the fuel injection computer) matched to the operatingcycles of the fuel injection valves, maximum design speeds of the engineand the like. In a typical four-cylinder engine, having a maximumpermissible speed of 6,500 rpm, the following pulse repetition rates, orfrequencies are suitable:

tion pulse, or the fuel injection terminate pulse determines the lengthof the open time of the injection valve; after the terminate pulse hasbeen applied, a l-signal is placed on terminal 302', which is connectedthrough switch 150 to the J input of FF 152. Alternatively, oradditionally, at a time determined in accordance with the electroniccircuitry of the fuel injection system, a

l-signal is applied to terminal 302 to reliably ensure starting of fuelinjection. The pulse of terminal 302 may occur before, or after closingof switch 150, since exact synchronism may not be obtainable in allinstances for structural reasons. An electronic control system with 6which the present application can be used is described in co-pendingapplication Ser. 3,65';729, filed May 31, 1973, now U.S. Pat. No.-3,898,962, assigned to the assignee of the present application. Weclaim:I

1. Governor arrangement for an internal combustion engine, having anelectronic control system including a digital circuit providing fuelsupply and fuel tennination signals to the engine, and means (41)providing a speed signal ()3) having a frequency proportional to enginespeed, said governor arrangement comprising means (62a) providing areference signal frequency proportional to maximum permissible governedengine speed;

comparator means (98a) having said speed signal 3) and said referencesignal (f applied thereto and providing an output signal when thefrequency of the speed signal exceeds the frequency of the referencesignal;

a digital switch (152) connected to control termination of fuel supplyto the engine when controlled to change state, the output signal fromsaid comparator means (98a) being connected to the digital switch tocause said switch to change state when said output signal from thecomparator means is generated; and

pulse scanning or strobing circuits (97, 97a) connected to said speedsignal generating means (41) and said reference signal generating means(62a), respectively, and equalizing the pulse durations of the signalsprovided by said respective signal generating means.

2. Arrangement according to claim 1, wherein the fuel control comprisesa fuel injection system (153, 32) 35 in which the duration of the fuelinjection pulses determines the amount of fuel being applied to theengine, said duration being defined when said switch changes to one(set) state and terminating when said switch changes to the other(re-set) state.

3. Arrangement according to claim 1, wherein the comparator means (98a)comprises a comparator stage including an EXCLUSlVE OR-gate.

4. Arrangement according to claim 1, wherein the comparator meanscomprises an EXCLUSIVE OR- 45 gate having two inputs, one input, each,being connected to the output of a respective pulse scanning or strobingcircuit.

5. Arrangement according to claim 1, wherein at least one of the pulsescanning or strobing circuits (97, 97a) comprises two D-tlip-flops (167,170; 172a, 172); a strobe pulse source (168, 169) connected to the clockinputs of both the flip flops;

the D input of the first D-FF (167, 172a) having the input frequencyapplied thereto;

and a NAND-gate (171, 173) having its inputs connected to the output ofthe first D-flip-flop (167, 1720) and the further input connected to theinverse output of the second D-flip-flop (170, 172).

6. Arrangement according to claim 1, wherein said digital switchcomprises a JK-flip-tlop (152).

7. Arrangement according to claim 1, wherein the electronic controlsystem provides a control pulse defining termination of fuel supply, ata given instant of 65 time (terminal 301);

means (300) connecting said terminate pulse to said digital switch tocontrol said digital switch to terminate fuel supply to the engine;

8 stant of generation of the output signal from said comparator meansand regardless of presence of a terminate pulse from said electroniccontrol system.

1. Governor arrangement for an internal combustion engine, having anelectronic control system including a digital circuit providing fuelsupply and fuel termination signals to the engine, and means (41)providing a speed signal (f3) having a frequency proportional to enginespeed, said governor arrangement comprising means (62a) providing areference signal frequEncy proportional to maximum permissible governedengine speed; comparator means (98a) having said speed signal (f3) andsaid reference signal (fr) applied thereto and providing an outputsignal when the frequency of the speed signal exceeds the frequency ofthe reference signal; a digital switch (152) connected to controltermination of fuel supply to the engine when controlled to changestate, the output signal from said comparator means (98a) beingconnected to the digital switch to cause said switch to change statewhen said output signal from the comparator means is generated; andpulse scanning or strobing circuits (97, 97a) connected to said speedsignal generating means (41) and said reference signal generating means(62a), respectively, and equalizing the pulse durations of the signalsprovided by said respective signal generating means.
 2. Arrangementaccording to claim 1, wherein the fuel control comprises a fuelinjection system (153, 32) in which the duration of the fuel injectionpulses determines the amount of fuel being applied to the engine, saidduration being defined when said switch changes to one (set) state andterminating when said switch changes to the other (re-set) state. 3.Arrangement according to claim 1, wherein the comparator means (98a)comprises a comparator stage including an EXCLUSIVE OR-gate. 4.Arrangement according to claim 1, wherein the comparator means comprisesan EXCLUSIVE OR-gate having two inputs, one input, each, being connectedto the output of a respective pulse scanning or strobing circuit. 5.Arrangement according to claim 1, wherein at least one of the pulsescanning or strobing circuits (97, 97a) comprises two D-flip-flops (167,170; 172a, 172); a strobe pulse source (168, 169) connected to the clockinputs of both the flip-flops; the D input of the first D-FF (167, 172a)having the input frequency applied thereto; and a NAND-gate (171, 173)having its inputs connected to the output of the first D-flip-flop (167,172a) and the further input connected to the inverse output of thesecond D-flip-flop (170, 172).
 6. Arrangement according to claim 1,wherein said digital switch comprises a JK-flip-flop (152). 7.Arrangement according to claim 1, wherein the electronic control systemprovides a control pulse defining termination of fuel supply, at a giveninstant of time (terminal 301); means (300) connecting said''''terminate'''' pulse to said digital switch to control said digitalswitch to terminate fuel supply to the engine; and wherein the outputsignal from said comparator means (98a) is connected to said connectionmeans (300) to provide a signal to said digital switch and cause saiddigital switch to change state and terminate fuel supply to the engineat the instant of generation of the output signal from said comparatormeans and regardless of presence of a terminate pulse from saidelectronic control system.